If I was the owner I'd be pissed at the agent that they showed a heap of potential clients how much of a dump your house is. They will probably have to redo the whole process after you guys have left. In Australia you would have to be given several weeks notice before they did something like this. Perhaps because your housemates neglect everything, perhaps they neglected to check the mail or realise there was notice amongst the mail? Part of me just thinks you guys are so sloppy at everything that you don't even realise things.